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D5435-13 – Standard Test Method Technical Guide
🧪 Overview and Scope
This test method covers the determination of quantity (Q) and intensity (I) results for several elements in soils, spoils, fly-ash, and other soil substitutes to ascertain their suitability for the growth of vegetation and possible adverse effects of metals on the food chain. The values stated in SI units are to be regarded as standard. All measured and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026.
This standard does not purport to address all safety problems; it is the responsibility of the user to establish appropriate safety and health practices and determine regulatory limitations.
⚙️ Test Method Procedure
A representative sample material to be tested is air dried, sieved to pass a 2-mm screen, and equilibrated for 16 to 20 h with the soil test solution containing the optimum activities (I) of H3O+, Ca++, Mg++, K+, and DTPA (diethylenetriaminepentaacetate) to render a small exchange of metals from the solid phase to the solution phase. This test method is calibrated with respect to pH, K, Ca, Mg, H/(Ca + Mg)1/2, Mg/K, Ca/Mg, Mn, Fe, Cu, Zn, Al, Pb, Ni, and Cd. In addition to the exchangeable or labile amounts (Q), or both, of the same elements, comparable levels of the negative logarithm values analogous to pH may be calculated using the ligand constants for the respective elements.
📊 Key Parameters and Calibration
The table below lists the elements and parameters determined by this test method:
| 🟦 Element | 📏 Parameter | 🎯 Role |
|---|---|---|
| pH (H3O+) | Intensity (I) | Measure of soil acidity |
| Potassium (K) | Intensity (I) | Essential nutrient availability |
| Calcium (Ca) | Intensity (I) | Essential nutrient availability |
| Magnesium (Mg) | Intensity (I) | Essential nutrient availability |
| Manganese (Mn) | Quantity (Q)/Intensity (I) | Nutrient or toxic element |
| Iron (Fe) | Quantity (Q)/Intensity (I) | Nutrient or toxic element |
| Copper (Cu) | Quantity (Q)/Intensity (I) | Nutrient or toxic element |
| Zinc (Zn) | Quantity (Q)/Intensity (I) | Nutrient or toxic element |
| Aluminum (Al) | Quantity (Q)/Intensity (I) | Potentially toxic element |
| Lead (Pb) | Quantity (Q)/Intensity (I) | Toxic heavy metal |
| Nickel (Ni) | Quantity (Q)/Intensity (I) | Toxic heavy metal |
| Cadmium (Cd) | Quantity (Q)/Intensity (I) | Toxic heavy metal |
Additionally, ratios such as H/(Ca + Mg)1/2, Mg/K, and Ca/Mg are used for calibration.
💡 Tip: This test method has been used to evaluate synthetic soils from fly-ash and for monitoring sewage sludge effects on land for essential elements without food chain harm.
⚡ Important: Ensure that all measured and calculated values conform to Practice D6026 for significant digits and rounding.
❓ Frequently Asked Questions
🔍 What does this test method determine?
It determines the quantity (Q) and intensity (I) results for several elements in soils and soil substitutes to assess their suitability for plant growth and food chain protection.
💡 Why are Q and I parameters important?
Bioavailability of chemical elements is poorly related to total chemical composition. The intensity (I) and quantity (Q) provide a better measure of essential and toxic element availability for plants.
⚡ How is the sample prepared for testing?
The representative sample is air-dried, sieved to pass a 2-mm screen, and equilibrated for 16 to 20 hours with a soil test solution containing optimized activities of H3O+, Ca++, Mg++, K+, and DTPA.
📌 What elements are calibrated in this method?
The method is calibrated for pH, K, Ca, Mg, and the metals Mn, Fe, Cu, Zn, Al, Pb, Ni, and Cd, along with ratios like H/(Ca + Mg)1/2.